Multiple Choice
Which of the following types of DNA is the most common DNA form?
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7. DNA and Chromosome Structure
Alternative DNA Forms
Multiple Choice
In the context of alternative DNA forms, which conformation is considered the relaxed (low-energy, physiological) form of DNA under typical cellular conditions?
A
Z-DNA (left-handed helix favored by alternating purine-pyrimidine sequences)
B
B-DNA (right-handed helix with ~10.5 bp per turn)
C
G-quadruplex DNA (four-stranded structure stabilized by guanine tetrads)
D
A-DNA (right-handed, dehydrated form commonly found in DNA-RNA hybrids)
Verified step by step guidance1
Understand that DNA can adopt multiple conformations depending on environmental conditions such as hydration, sequence, and ionic strength.
Recall that B-DNA is the most common form of DNA under physiological (normal cellular) conditions, characterized by a right-handed helix with approximately 10.5 base pairs per turn.
Recognize that A-DNA is a right-handed helix as well but is typically found under dehydrated conditions or in DNA-RNA hybrids, making it less common in living cells.
Note that Z-DNA is a left-handed helix favored by specific sequences (alternating purine-pyrimidine) and is usually transient and less stable under normal conditions.
Identify that G-quadruplex DNA is a specialized four-stranded structure stabilized by guanine tetrads, not the relaxed form of DNA in typical cells.
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